/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * libc/stdio/lib_libfflush.c
 *
 *   Copyright (C) 2007-2008, 2011-2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdbool.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

#include <tinyara/fs/fs.h>

#include "lib_internal.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Global Constant Data
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Constant Data
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: lib_fflush
 *
 * Description:
 *  The function lib_fflush() forces a write of all user-space buffered data for
 *  the given output or update stream via the stream's underlying write
 *  function.  The open status of the stream is unaffected.
 *
 * Parmeters:
 *  stream - the stream to flush
 *  bforce - flush must be complete.
 *
 * Return:
 *  A negated errno value on failure, otherwise the number of bytes remaining
 *  in the buffer.
 *
 ****************************************************************************/

ssize_t lib_fflush(FAR FILE *stream, bool bforce)
{
#if CONFIG_STDIO_BUFFER_SIZE > 0
	FAR const unsigned char *src;
	ssize_t bytes_written;
	ssize_t nbuffer;

	/* Return EBADF if the file is not opened for writing */

	if (stream->fs_fd < 0 || (stream->fs_oflags & O_WROK) == 0) {
		return -EBADF;
	}

	/* Make sure that we have exclusive access to the stream */

	lib_take_semaphore(stream);

	/* Make sure that the buffer holds valid data */

	if (stream->fs_bufpos != stream->fs_bufstart) {
		/* Make sure that the buffer holds buffered write data.  We do not
		 * support concurrent read/write buffer usage.
		 */

		if (stream->fs_bufread != stream->fs_bufstart) {
			/* The buffer holds read data... just return zero meaning "no bytes
			 * remaining in the buffer."
			 */

			lib_give_semaphore(stream);
			return 0;
		}

		/* How many bytes of write data are used in the buffer now */

		nbuffer = stream->fs_bufpos - stream->fs_bufstart;

		/* Try to write that amount */

		src = stream->fs_bufstart;
		do {
			/* Perform the write */

			bytes_written = write(stream->fs_fd, src, nbuffer);
			if (bytes_written < 0) {
				/* Write failed.  The cause of the failure is in 'errno'.
				 * returned the negated errno value.
				 */

				stream->fs_flags |= __FS_FLAG_ERROR;
				lib_give_semaphore(stream);
				return -get_errno();
			}

			/* Handle partial writes.  fflush() must either return with
			 * an error condition or with the data successfully flushed
			 * from the buffer.
			 */

			src += bytes_written;
			nbuffer -= bytes_written;
		} while (bforce && nbuffer > 0);

		/* Reset the buffer position to the beginning of the buffer */

		stream->fs_bufpos = stream->fs_bufstart;

		/* For the case of an incomplete write, nbuffer will be non-zero
		 * It will hold the number of bytes that were not written.
		 * Move the data down in the buffer to handle this (rare) case
		 */

		while (nbuffer) {
			*stream->fs_bufpos++ = *src++;
			--nbuffer;
		}
	}

	/* Restore normal access to the stream and return the number of bytes
	 * remaining in the buffer.
	 */

	lib_give_semaphore(stream);
	return stream->fs_bufpos - stream->fs_bufstart;
#else
	/* Return no bytes remaining in the buffer */

	return 0;
#endif
}
